Platinum‐Catalyzed Hydrofluorination of Alkynes: Hydrogen Bonding to Indolylphosphine Ligands to Provide Fluoride Reactivity

The reaction of the Pt complexes cis‐[Pt(CH(3))(2){R(2)P(Ind)}(2)] (Ind=2‐(3‐methyl)indolyl, R=Ph (1 a), 4‐FC(6)H(4) (1 b), 4‐CF(3)C(6)H(4) (1 c)) with HF afforded the fluorido complexes trans‐[Pt(F(HF)(2))(CH(3)){R(2)P(Ind)}(2)] 2 a–c, which can be converted into trans‐[Pt(F)(CH(3)){R(2)P(Ind)}(2)] (3 a–c) by treatment with CsF. Addition of 3‐hexyne to 2 a–c gave alkyne complexes trans‐[Pt(C,C‐η(2) ‐C(2)H(5) C≡CC(2)H(5))(CH(3)){R(2)P(Ind)}(2){F(HF)(2)}] (4 a–c) at which a fluoride is stabilised as polyfluoride in the coordination sphere by hydrogen bonding to the indolyl‐substituted phosphine ligands. Subsequent heating of a solution of 4 a in the presence of PVPHF led to fluoroalkene formation. Selective catalytic hydrofluorination of alkynes to yield (Z)‐fluoroalkenes were developed. The ability of hydrogen bonding to polyfluoride favours the fluorination step as demonstrated by studies with complexes bearing no indolyl groups at the phosphine ligands.